1. Field of the Invention
The present invention relates to a printing system, and relates in particular to a printing system appropriate for outputting, through a computer to a printer, digital data obtained by a digital still camera or a video camera, or for printing such digital data through a recording medium or communication means.
2. Related Background Art
Conventionally, thermal transfer line printers are available that employ thermal recording paper for printing, that selectively drive multiple heat generating elements arranged in the main scanning direction to feed paper in the sub-scanning direction, and that print lines of dots on the paper.
As a consequence of the development of input devices such as digital cameras, digital video cameras or scanners for handling images the focus has been on the use of thermal transfer printers as printing means.
The reason for this is as follows. Because with an ink-jet printer there are only two choices, either ink droplets are ejected or they are not, resolution and the appearance of tone gradation are obtained by depositing small droplets of ink on paper. On the other hand, with a thermal transfer printer, since the value of the available heat can easily be changed for each pixel, many tone gradations can be obtained for one pixel, and when compared with an ink-jet printer, a thermal transfer printer can print a smoother, higher quality image. Further, as the functions of thermal heads and the quality of the printed material they output are improved, images for which the quality of the finish is as good as that of a silver halide photograph can be printed. Therefore, thermal transfer printers have drawn much attention, especially as a natural image printer that can keep step with the recent progress of digital cameras.
Recently, a system has also appeared that provides for one of the above printing apparatuses to be directly connected to an image pickup device, such as a digital camera or a digital video camera, or to be integrally constructed with a device, so that obtained image data can be printed without an apparatus, such as a computer, being required for processing the data. This system, since image data obtained by a digital camera or a digital video camera can be easily printed, like a photograph, it is very convenient.
As an example of this system, the connection of an image input device and an image output device is described in Japanese Application Laid-Open No. 10-243327.
According to this publication, in an image input/output system wherein an image output device and an image input device are connected together, the image output device has a function for receiving an image signal from the image input signal and outputting it, and includes a power source for supplying power to the image input device. The image output device includes: determination means, which is connected to the image output device by a connection cable along which image data is transmitted and power is received from the image output device, and which determines whether the supply of power by the image output device is enabled; and a power source. When the determination means ascertains that the supply of power by the image output device has been enabled, it employs that power. But when the supply of power has not been enabled, the determination means employs the power available from the power source. According to this system, since power can be received from the image output device, an image can be printed without taking into account the remaining power available in the image input device, such as a digital camera.
Further, in Japanese Patent Application Laid-Open No. 9-65182, a power conservation system for a composite camera is described. According to this publication, the composite camera is designed by integrally forming an image pickup means, which includes a digital viewfinder, for storing video data on a recording medium, and a printing means for printing the video data on recording paper. The composite camera also comprises control means for halting the supply of power to the electronic viewfinder while the printing means is outputting the video data to the recording paper. According to the specifications for this camera, since the supply of power to the electronic viewfinder is halted during printing, an effective power saving configuration is provided.
In addition, since the digital camera is directly connected to the printer, while the printer is using image data acquired by the digital camera for printing, a power supply device, such as an AC adaptor, that is used to supply power to the printer can also be used to supply power to the digital camera when requested. However, in accordance with the recent development of more power efficient semiconductors, the consumption of power can be reduced, so that a battery can be used to operate both the digital camera and the printer, and the two can be employed outdoors as a mobile device.
Furthermore, information concerning the images to be printed, the number of sheets to be printed and the printing method to be used can be set in advance in the digital camera, so that once printing is started, multiple types of images that have been designated in advance can be automatically produced.
However, a problem has arisen in that when the digital camera and the printer are employed as mobile devices, especially when it is necessary for a large number of sheets to be printed, the battery power is soon exhausted and the printing is halted.
Further, as another problem, due to a shortage of paper the printing process may be interrupted before the previously designated printing has been completed.
In both these cases, when resuming printing, the process must be begun again at the beginning, or the setup procedure for the printing must be repeated.
As a result, since each time a continuous printing process is interrupted the printing must be resumed at the beginning, not only is paper and ink wasted, but also time.
In addition, a certain amount of labor is required to select only those images that have not yet been printed or to repeat the printing setup procedure, and there is always a chance that an error may be made in the selection of the images or in the designation of the number of sheets to be printed and that, as a result, paper, ink and time will again be wasted. Furthermore, when the requirement is for a large number of sheets to be printed, the above problems become more significant, making it impossible to provide a convenient printing system for users.